1. Field of the Invention
The present invention relates to a racket frame, and more particularly to a racket frame with a prestressing device to provide an enhanced structure.
2. Description of Related Art
With reference to FIG. 9, a conventional racket frame (60) is made of carbon fiber and epoxy resin composite and used for playing with a tennis ball or a paddleball and has a head hoop (61), a connecting segment (62) and a handle (63).
The head hoop (61) is connected with a string (611) and has an inner surface and a bottom end. The string (611) is wound on the inner surface of the head hoop (61) in a crisscross manner.
The connecting segment (62) is connected with the head hoop (61) and has a yoke (621), two shafts (622) and a throat (623). The yoke (621) is formed on the bottom end of the head hoop (61). The shafts (622) are arc shaped, are respectively mounted with the yoke (621) and each shaft (622) has an upper end, a lower end, a front side and a rear side. The upper ends of the shafts (622) are respectively connected to the yoke (621). The throat (623) is connected to the lower ends of the shafts (622).
The handle (63) is connected with the connecting segment (62) and has a proximal end. The proximal end of the handle (63) is connected with the throat (623).
When the tennis ball or a paddleball hitting on the string (611), the front sides of the shafts (622) bear a tensile stress and the rear sides of the shafts (622) bear a compressive stress because the shafts (622) are made of material of carbon fiber and epoxy resin composite. The material has a property that its tensile strength is much better than the its compressive strength. So the conventional racket frame (60) always broken from the compressed side if the conventional racket frame (60) was broken cause by overloading.
The invention provides a racket frame that can mitigate or obviate the aforementioned problems.